Method and device for transmitting data unit, and method and device for receiving data unit

ABSTRACT

A transmitting device generates a medium access control (MAC) protocol data unit (PDU), and transmits the MAC PDU. The transmitting device generates the MAC PDU such that the MAC PDU includes at least a MAC service data unit (SDU) and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC control element (CE) and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2018/000841, filed on Jan. 18, 2018, which claims the benefit of U.S. Provisional Application No. 62/447,881, filed on Jan. 18, 2017, the contents of which are hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, and more particularly, to a method for transmitting or receiving a data unit and an apparatus therefor.

BACKGROUND ART

As an example of a mobile communication system to which the present invention is applicable, a 3rd Generation Partnership Project Long Term Evolution (hereinafter, referred to as LTE) communication system is described in brief.

FIG. 1 is a view schematically illustrating a network structure of an E-UMTS as an exemplary radio communication system. An Evolved Universal Mobile Telecommunications System (E-UMTS) is an advanced version of a conventional Universal Mobile Telecommunications System (UMTS) and basic standardization thereof is currently underway in the 3GPP. E-UMTS may be generally referred to as a Long Term Evolution (LTE) system. For details of the technical specifications of the UMTS and E-UMTS, reference can be made to Release 7 and Release 8 of “3rd Generation Partnership Project; Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs (eNBs), and an Access Gateway (AG) which is located at an end of the network (E-UTRAN) and connected to an external network. The eNBs may simultaneously transmit multiple data streams for a broadcast service, a multicast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in one of bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides a downlink (DL) or uplink (UL) transmission service to a plurality of UEs in the bandwidth. Different cells may be set to provide different bandwidths. The eNB controls data transmission or reception to and from a plurality of UEs. The eNB transmits DL scheduling information of DL data to a corresponding UE so as to inform the UE of a time/frequency domain in which the DL data is supposed to be transmitted, coding, a data size, and hybrid automatic repeat and request (HARQ)-related information. In addition, the eNB transmits UL scheduling information of UL data to a corresponding UE so as to inform the UE of a time/frequency domain which may be used by the UE, coding, a data size, and HARQ-related information. An interface for transmitting user traffic or control traffic may be used between eNBs. A core network (CN) may include the AG and a network node or the like for user registration of UEs. The AG manages the mobility of a UE on a tracking area (TA) basis. One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTE based on wideband code division multiple access (WCDMA), the demands and expectations of users and service providers are on the rise. In addition, considering other radio access technologies under development, new technological evolution is required to secure high competitiveness in the future. Decrease in cost per bit, increase in service availability, flexible use of frequency bands, a simplified structure, an open interface, appropriate power consumption of UEs, and the like are required.

As more and more communication devices demand larger communication capacity, there is a need for improved mobile broadband communication compared to existing RAT. Also, massive machine type communication (MTC), which provides various services by connecting many devices and objects, is one of the major issues to be considered in the next generation communication. In addition, a communication system design considering a service/UE sensitive to reliability and latency is being discussed. The introduction of next-generation RAT, which takes into account such advanced mobile broadband communication, massive MTC (mMCT), and ultra-reliable and low latency communication (URLLC), is being discussed.

DISCLOSURE Technical Problem

Due to introduction of new radio communication technology, the number of user equipments (UEs) to which a BS should provide a service in a prescribed resource region increases and the amount of data and control information that the BS should transmit to the UEs increases. Since the amount of resources available to the BS for communication with the UE(s) is limited, a new method in which the BS efficiently receives/transmits uplink/downlink data and/or uplink/downlink control information using the limited radio resources is needed.

With development of technologies, overcoming delay or latency has become an important challenge. Applications whose performance critically depends on delay/latency are increasing. Accordingly, a method to reduce delay/latency compared to the legacy system is demanded.

Also, a method for transmitting/receiving signals effectively in a system supporting new radio access technology is required.

The technical objects that can be achieved through the present invention are not limited to what has been particularly described hereinabove and other technical objects not described herein will be more clearly understood by persons skilled in the art from the following detailed description.

Technical Solution

In an aspect of the present invention, provided herein is a method of transmitting, by a transmitting device, a data unit in a wireless communication system. The method comprises: generating, by the transmitting device, a medium access control (MAC) protocol data unit (PDU); and transmitting, by the transmitting device, the MAC PDU. The MAC PDU is generated such that the MAC PDU includes at least a MAC service data unit (SDU) and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC control element (CE) and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE.

In another aspect of the present invention, provided herein is a method of receiving, by a receiving device, a data unit in a wireless communication system. The method comprises: receiving, by the receiving device, a medium access control (MAC) protocol data unit (PDU); and processing, by the receiving device, the MAC PDU. The MAC PDU includes at least a MAC service data unit (SDU) and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC control element (CE) and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE. The receiving device processes the MAC PDU from the end of the MAC PDU toward the start of the MAC PDU.

In a further another aspect of the present invention, provided herein is a transmitting device for transmitting a data unit in a wireless communication system. The transmitting device comprises: a radio frequency (RF) unit, and a processor configured to control the RF unit. The processor may be configured to: generate a medium access control (MAC) protocol data unit (PDU); and control the RF unit to transmit the MAC PDU. The processor may generate the MAC PDU such that the MAC PDU includes at least a MAC service data unit (SDU) and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC control element (CE) and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE.

In a still further aspect of the present invention, provided herein is a receiving device for receiving a data unit in a wireless communication system. The receiving device comprises: a radio frequency (RF) unit, and a processor configured to control the RF unit. The processor may be configured to: control the RF unit to receive a medium access control (MAC) protocol data unit (PDU); and process the MAC PDU. The MAC PDU includes at least a MAC service data unit (SDU) and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC control element (CE) and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE. The processor may be configured to process the MAC PDU from the end of the MAC PDU toward the start of the MAC PDU.

In each aspect of the present invention, the first MAC subheader may include a logical channel identity (LCID) field which identifies a logical channel or radio link control (RLC) entity to which the MAC SDU belongs, and a length (L) field which indicates a length of the MAC SDU.

In each aspect of the present invention, the second MAC subheader may include a LCID field which identifies a type of the MAC CE.

In each aspect of the present invention, the second MAC subheader may include a L field which indicates a length of the MAC CE.

In each aspect of the present invention, the second MAC subheader may include the LCID field after the L field.

In each aspect of the present invention, the MAC PDU may include the MAC SDU and the first MAC subheader before the MAC CE and the second MAC subheader.

In each aspect of the present invention, the MAC PDU may include the MAC CE and the second MAC subheader in the end of the MAC PDU.

In each aspect of the present invention, the transmitting or receiving device is an autonomous vehicle that communicates with at least a mobile terminal, a network, and another autonomous vehicle other than the device. The above technical solutions are merely some parts of the embodiments of the present invention and various embodiments into which the technical features of the present invention are incorporated can be derived and understood by persons skilled in the art from the following detailed description of the present invention.

Advantageous Effects

According to the present invention, radio communication signals can be efficiently transmitted/received. Therefore, overall throughput of a radio communication system can be improved.

According to one embodiment of the present invention, a low cost/complexity UE can perform communication with a base station (BS) at low cost while maintaining compatibility with a legacy system.

According to one embodiment of the present invention, the UE can be implemented at low cost/complexity.

According to one embodiment of the present invention, the UE and the BS can perform communication with each other at a narrowband.

According to an embodiment of the present invention, delay/latency occurring during communication between a user equipment and a BS may be reduce.

According to the present invention, a transmitting side can process medium access control (MAC) service data units (SDUs) for transmission without waiting for the MAC control element (CE) construction, thereby facilitating the fast MAC PDU processing in the transmitting side.

According to the present invention, a receiving side can easily identify a MAC CE by processing a MAC protocol data unit (PDU) from the end to start of the MAC PDU, and this will facilitate the fast MAC CE processing in the receiving side.

Also, signals in a new radio access technology system can be transmitted/received effectively.

It will be appreciated by persons skilled in the art that that the effects that can be achieved through the present invention are not limited to what has been particularly described hereinabove and other advantages of the present invention will be more clearly understood from the following detailed description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention.

FIG. 1 is a view schematically illustrating a network structure of an E-UMTS as an exemplary radio communication system.

FIG. 2 is a block diagram illustrating network structure of an evolved universal mobile telecommunication system (E-UMTS).

FIG. 3 is a block diagram depicting architecture of a typical E-UTRAN and a typical EPC.

FIG. 4 is a diagram showing a control plane and a user plane of a radio interface protocol between a UE and an E-UTRAN based on a 3GPP radio access network standard.

FIG. 5 is a view showing an example of a physical channel structure used in an E-UMTS system.

FIG. 6 is a diagram for medium access control (MAC) structure overview in a UE side.

FIG. 7 is a diagram for a MAC PDU structure used in the LTE/LTE-A system.

FIG. 8 are examples of MAC subheaders used in the LTE/LTE-A system.

FIG. 9 illustrates an overall procedure of the MAC PDU construction process in the LTE/LTE-A system.

FIG. 10 illustrates an example of a MAC PDU construction process for the NR system according to the present invention.

FIG. 11 is a block diagram illustrating elements of a transmitting device 100 and a receiving device 200 for implementing the present invention.

MODE FOR INVENTION

Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention, rather than to show the only embodiments that can be implemented according to the invention. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without such specific details.

In some instances, known structures and devices are omitted or are shown in block diagram form, focusing on important features of the structures and devices, so as not to obscure the concept of the present invention. The same reference numbers will be used throughout this specification to refer to the same or like parts.

The following techniques, apparatuses, and systems may be applied to a variety of wireless multiple access systems. Examples of the multiple access systems include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, and a multicarrier frequency division multiple access (MC-FDMA) system. CDMA may be embodied through radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be embodied through radio technology such as global system for mobile communications (GSM), general packet radio service (GPRS), or enhanced data rates for GSM evolution (EDGE). OFDMA may be embodied through radio technology such as institute of electrical and electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA (E-UTRA). UTRA is a part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA in DL and SC-FDMA in UL. LTE-advanced (LTE-A) is an evolved version of 3GPP LTE. For convenience of description, it is assumed that the present invention is applied to 3GPP LTE/LTE-A. However, the technical features of the present invention are not limited thereto. For example, although the following detailed description is given based on a mobile communication system corresponding to a 3GPP LTE/LTE-A system, aspects of the present invention that are not specific to 3GPP LTE/LTE-A are applicable to other mobile communication systems.

For example, the present invention is applicable to contention based communication such as Wi-Fi as well as non-contention based communication as in the 3GPP LTE/LTE-A system in which an eNB allocates a DL/UL time/frequency resource to a UE and the UE receives a DL signal and transmits a UL signal according to resource allocation of the eNB. In a non-contention based communication scheme, an access point (AP) or a control node for controlling the AP allocates a resource for communication between the UE and the AP, whereas, in a contention based communication scheme, a communication resource is occupied through contention between UEs which desire to access the AP. The contention based communication scheme will now be described in brief. One type of the contention based communication scheme is carrier sense multiple access (CSMA). CSMA refers to a probabilistic media access control (MAC) protocol for confirming, before a node or a communication device transmits traffic on a shared transmission medium (also called a shared channel) such as a frequency band, that there is no other traffic on the same shared transmission medium. In CSMA, a transmitting device determines whether another transmission is being performed before attempting to transmit traffic to a receiving device. In other words, the transmitting device attempts to detect presence of a carrier from another transmitting device before attempting to perform transmission. Upon sensing the carrier, the transmitting device waits for another transmission device which is performing transmission to finish transmission, before performing transmission thereof. Consequently, CSMA can be a communication scheme based on the principle of “sense before transmit” or “listen before talk”. A scheme for avoiding collision between transmitting devices in the contention based communication system using CSMA includes carrier sense multiple access with collision detection (CSMA/CD) and/or carrier sense multiple access with collision avoidance (CSMA/CA). CSMA/CD is a collision detection scheme in a wired local area network (LAN) environment. In CSMA/CD, a personal computer (PC) or a server which desires to perform communication in an Ethernet environment first confirms whether communication occurs on a network and, if another device carries data on the network, the PC or the server waits and then transmits data. That is, when two or more users (e.g. PCs, UEs, etc.) simultaneously transmit data, collision occurs between simultaneous transmission and CSMA/CD is a scheme for flexibly transmitting data by monitoring collision. A transmitting device using CSMA/CD adjusts data transmission thereof by sensing data transmission performed by another device using a specific rule. CSMA/CA is a MAC protocol specified in IEEE 802.11 standards. A wireless LAN (WLAN) system conforming to IEEE 802.11 standards does not use CSMA/CD which has been used in IEEE 802.3 standards and uses CA, i.e. a collision avoidance scheme. Transmission devices always sense carrier of a network and, if the network is empty, the transmission devices wait for determined time according to locations thereof registered in a list and then transmit data. Various methods are used to determine priority of the transmission devices in the list and to reconfigure priority. In a system according to some versions of IEEE 802.11 standards, collision may occur and, in this case, a collision sensing procedure is performed. A transmission device using CSMA/CA avoids collision between data transmission thereof and data transmission of another transmission device using a specific rule.

In the present invention, the term “assume” may mean that a subject to transmit a channel transmits the channel in accordance with the corresponding “assumption.” This may also mean that a subject to receive the channel receives or decodes the channel in a form conforming to the “assumption,” on the assumption that the channel has been transmitted according to the “assumption.”

In the present invention, a user equipment (UE) may be a fixed or mobile device. Examples of the UE include various devices that transmit and receive user data and/or various kinds of control information to and from a base station (BS). The UE may be referred to as a terminal equipment (TE), a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, a personal digital assistant (PDA), a wireless modem, a handheld device, etc. In addition, in the present invention, a BS generally refers to a fixed station that performs communication with a UE and/or another BS, and exchanges various kinds of data and control information with the UE and another BS. The BS may be referred to as an advanced base station (ABS), a node-B (NB), an evolved node-B (eNB), a base transceiver system (BTS), an access point (AP), a processing server (PS), etc. Especially, a BS of the UMTS is referred to as a NB, a BS of the EPC/LTE is referred to as an eNB, and a BS of the new radio (NR) system is referred to as a gNB. For convenience of description, in describing the present invention, a BS will be referred to as an eNB.

In the present invention, a node refers to a fixed point capable of transmitting/receiving a radio signal through communication with a UE. Various types of eNBs may be used as nodes irrespective of the terms thereof. For example, a BS, a node B (NB), an e-node B (eNB), a pico-cell eNB (PeNB), a home eNB (HeNB), a relay, a repeater, etc. may be a node. In addition, the node may not be an eNB. For example, the node may be a radio remote head (RRH) or a radio remote unit (RRU). The RRH or RRU generally has a lower power level than a power level of an eNB. Since the RRH or RRU (hereinafter, RRH/RRU) is generally connected to the eNB through a dedicated line such as an optical cable, cooperative communication between RRH/RRU and the eNB can be smoothly performed in comparison with cooperative communication between eNBs connected by a radio line. At least one antenna is installed per node. The antenna may mean a physical antenna or mean an antenna port or a virtual antenna.

In the present invention, a cell refers to a prescribed geographical area to which one or more nodes provide a communication service. Accordingly, in the present invention, communicating with a specific cell may mean communicating with an eNB or a node which provides a communication service to the specific cell. In addition, a DL/UL signal of a specific cell refers to a DL/UL signal from/to an eNB or a node which provides a communication service to the specific cell. A node providing UL/DL communication services to a UE is called a serving node and a cell to which UL/DL communication services are provided by the serving node is especially called a serving cell.

Meanwhile, a 3GPP LTE/LTE-A system uses the concept of a cell in order to manage radio resources and a cell associated with the radio resources is distinguished from a cell of a geographic region.

A “cell” of a geographic region may be understood as coverage within which a node can provide service using a carrier and a “cell” of a radio resource is associated with bandwidth (BW) which is a frequency range configured by the carrier. Since DL coverage, which is a range within which the node is capable of transmitting a valid signal, and UL coverage, which is a range within which the node is capable of receiving the valid signal from the UE, depends upon a carrier carrying the signal, the coverage of the node may be associated with coverage of the “cell” of a radio resource used by the node. Accordingly, the term “cell” may be used to indicate service coverage of the node sometimes, a radio resource at other times, or a range that a signal using a radio resource can reach with valid strength at other times.

Meanwhile, the 3GPP LTE-A standard uses the concept of a cell to manage radio resources. The “cell” associated with the radio resources is defined by combination of downlink resources and uplink resources, that is, combination of DL component carrier (CC) and UL CC. The cell may be configured by downlink resources only, or may be configured by downlink resources and uplink resources. If carrier aggregation is supported, linkage between a carrier frequency of the downlink resources (or DL CC) and a carrier frequency of the uplink resources (or UL CC) may be indicated by system information. For example, combination of the DL resources and the UL resources may be indicated by linkage of system information block type 2 (SIB2). In this case, the carrier frequency means a center frequency of each cell or CC. A cell operating on a primary frequency may be referred to as a primary cell (Pcell) or PCC, and a cell operating on a secondary frequency may be referred to as a secondary cell (Scell) or SCC. The carrier corresponding to the Pcell on downlink will be referred to as a downlink primary CC (DL PCC), and the carrier corresponding to the Pcell on uplink will be referred to as an uplink primary CC (UL PCC). A Scell means a cell that may be configured after completion of radio resource control (RRC) connection establishment and used to provide additional radio resources. The Scell may form a set of serving cells for the UE together with the Pcell in accordance with capabilities of the UE. The carrier corresponding to the Scell on the downlink will be referred to as downlink secondary CC (DL SCC), and the carrier corresponding to the Scell on the uplink will be referred to as uplink secondary CC (UL SCC). Although the UE is in RRC-CONNECTED state, if it is not configured by carrier aggregation or does not support carrier aggregation, a single serving cell configured by the Pcell only exists.

In the present invention, “PDCCH” refers to a PDCCH, an EPDCCH (in subframes when configured), a MTC PDCCH (MPDCCH), for an RN with R-PDCCH configured and not suspended, to the R-PDCCH or, for NB-IoT to the narrowband PDCCH (NPDCCH).

In the present invention, monitoring a channel implies attempting to decode the channel. For example, monitoring a PDCCH implies attempting to decode PDCCH(s) (or PDCCH candidates).

In the present invention, for dual connectivity operation the term “special Cell” refers to the PCell of the master cell group (MCG) or the PSCell of the secondary cell group (SCG), otherwise the term Special Cell refers to the PCell. The MCG is a group of serving cells associated with a master eNB (MeNB) which terminates at least S1-MME, and the SCG is a group of serving cells associated with a secondary eNB (SeNB) that is providing additional radio resources for the UE but is not the MeNB. The SCG is comprised of a primary SCell (PSCell) and optionally one or more SCells. In dual connectivity, two MAC entities are configured in the UE: one for the MCG and one for the SCG. Each MAC entity is configured by RRC with a serving cell supporting PUCCH transmission and contention based Random Access. In this specification, the term SpCell refers to such cell, whereas the term SCell refers to other serving cells. The term SpCell either refers to the PCell of the MCG or the PSCell of the SCG depending on if the MAC entity is associated to the MCG or the SCG, respectively.

In the present invention, “C-RNTI” refers to a cell RNTI, “SI-RNTI” refers to a system information RNTI, “P-RNTI” refers to a paging RNTI, “RA-RNTI” refers to a random access RNTI, “SC-RNTI” refers to a single cell RNTI″, “SL-RNTI” refers to a sidelink RNTI, and “SPS C-RNTI” refers to a semi-persistent scheduling C-RNTI.

For terms and technologies which are not specifically described among the terms of and technologies employed in this specification, 3GPP LTE/LTE-A standard documents, for example, 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS 36.213, 3GPP TS 36.300, 3GPP TS 36.321, 3GPP TS 36.322, 3GPP TS 36.323 and 3GPP TS 36.331, and 3GPP NR standard documents, for example, 38.xxx series may be referenced.

FIG. 2 is a block diagram illustrating network structure of an evolved universal mobile telecommunication system (E-UMTS). The E-UMTS may be also referred to as an LTE system. The communication network is widely deployed to provide a variety of communication services such as voice (VoIP) through IMS and packet data.

As illustrated in FIG. 2, the E-UMTS network includes an evolved UMTS terrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC) and one or more user equipment. The E-UTRAN may include one or more evolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 may be located in one cell. One or more E-UTRAN mobility management entity (MME)/system architecture evolution (SAE) gateways 30 may be positioned at the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNB 20 to UE 10, and “uplink” refers to communication from the UE to an eNB.

FIG. 3 is a block diagram depicting architecture of a typical E-UTRAN and a typical EPC.

As illustrated in FIG. 3, an eNB 20 provides end points of a user plane and a control plane to the UE 10. MME/SAE gateway 30 provides an end point of a session and mobility management function for UE 10. The eNB and MME/SAE gateway may be connected via an S1 interface.

The eNB 20 is generally a fixed station that communicates with a UE 10, and may also be referred to as a base station (BS) or an access point. One eNB 20 may be deployed per cell. An interface for transmitting user traffic or control traffic may be used between eNBs 20.

The MME provides various functions including NAS signaling to eNBs 20, NAS signaling security, AS Security control, Inter CN node signaling for mobility between 3GPP access networks, Idle mode UE Reachability (including control and execution of paging retransmission), Tracking Area list management (for UE in idle and active mode), PDN GW and Serving GW selection, MME selection for handovers with MME change, SGSN selection for handovers to 2G or 3G 3GPP access networks, roaming, authentication, bearer management functions including dedicated bearer establishment, support for PWS (which includes ETWS and CMAS) message transmission. The SAE gateway host provides assorted functions including Per-user based packet filtering (by e.g. deep packet inspection), Lawful Interception, UE IP address allocation, Transport level packet marking in the downlink, UL and DL service level charging, gating and rate enforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAE gateway 30 will be referred to herein simply as a “gateway,” but it is understood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNB 20 and gateway 30 via the S1 interface. The eNBs 20 may be connected to each other via an X2 interface and neighboring eNBs may have a meshed network structure that has the X2 interface.

As illustrated, eNB 20 may perform functions of selection for gateway 30, routing toward the gateway during a Radio Resource Control (RRC) activation, scheduling and transmitting of paging messages, scheduling and transmitting of Broadcast Channel (BCCH) information, dynamic allocation of resources to UEs 10 in both uplink and downlink, configuration and provisioning of eNB measurements, radio bearer control, radio admission control (RAC), and connection mobility control in LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 may perform functions of paging origination, LTE-IDLE state management, ciphering of the user plane, System Architecture Evolution (SAE) bearer control, and ciphering and integrity protection of Non-Access Stratum (NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway (S-GW), and a packet data network-gateway (PDN-GW). The MME has information about connections and capabilities of UEs, mainly for use in managing the mobility of the UEs. The S-GW is a gateway having the E-UTRAN as an end point, and the PDN-GW is a gateway having a packet data network (PDN) as an end point.

FIG. 4 is a diagram showing a control plane and a user plane of a radio interface protocol between a UE and an E-UTRAN based on a 3GPP radio access network standard. The control plane refers to a path used for transmitting control messages used for managing a call between the UE and the E-UTRAN. The user plane refers to a path used for transmitting data generated in an application layer, e.g., voice data or Internet packet data.

Layer 1 (i.e. L1) of the LTE/LTE-A system is corresponding to a physical layer. A physical (PHY) layer of a first layer (Layer 1 or L1) provides an information transfer service to a higher layer using a physical channel. The PHY layer is connected to a medium access control (MAC) layer located on the higher layer via a transport channel. Data is transported between the MAC layer and the PHY layer via the transport channel. Data is transported between a physical layer of a transmitting side and a physical layer of a receiving side via physical channels. The physical channels use time and frequency as radio resources. In detail, the physical channel is modulated using an orthogonal frequency division multiple access (OFDMA) scheme in downlink and is modulated using a single carrier frequency division multiple access (SC-FDMA) scheme in uplink.

Layer 2 (i.e. L2) of the LTE/LTE-A system is split into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC) and Packet Data Convergence Protocol (PDCP). The MAC layer of a second layer (Layer 2 or L2) provides a service to a radio link control (RLC) layer of a higher layer via a logical channel. The RLC layer of the second layer supports reliable data transmission. A function of the RLC layer may be implemented by a functional block of the MAC layer. A packet data convergence protocol (PDCP) layer of the second layer performs a header compression function to reduce unnecessary control information for efficient transmission of an Internet protocol (IP) packet such as an IP version 4 (IPv4) packet or an IP version 6 (IPv6) packet in a radio interface having a relatively small bandwidth.

Layer 3 (i.e. L3) of the LTE/LTE-A system includes the following sublayers: Radio Resource Control (RRC) and Non Access Stratum (NAS). A radio resource control (RRC) layer located at the bottom of a third layer is defined only in the control plane. The RRC layer controls logical channels, transport channels, and physical channels in relation to configuration, re-configuration, and release of radio bearers (RBs). An RB refers to a service that the second layer provides for data transmission between the UE and the E-UTRAN. To this end, the RRC layer of the UE and the RRC layer of the E-UTRAN exchange RRC messages with each other. The non-access stratum (NAS) layer positioned over the RRC layer performs functions such as session management and mobility management.

Radio bearers are roughly classified into (user) data radio bearers (DRBs) and signaling radio bearers (SRBs). SRBs are defined as radio bearers (RBs) that are used only for the transmission of RRC and NAS messages.

One cell of the eNB is set to operate in one of bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplink transmission service to a plurality of UEs in the bandwidth. Different cells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN to the UE include a broadcast channel (BCH) for transmission of system information, a paging channel (PCH) for transmission of paging messages, and a downlink shared channel (SCH) for transmission of user traffic or control messages. Traffic or control messages of a downlink multicast or broadcast service may be transmitted through the downlink SCH and may also be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to the E-UTRAN include a random access channel (RACH) for transmission of initial control messages and an uplink SCH for transmission of user traffic or control messages. Logical channels that are defined above the transport channels and mapped to the transport channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic channel (MTCH).

FIG. 5 is a view showing an example of a physical channel structure used in an E-UMTS system. A physical channel includes several subframes on a time axis and several subcarriers on a frequency axis. Here, one subframe includes a plurality of symbols on the time axis. One subframe includes a plurality of resource blocks and one resource block includes a plurality of symbols and a plurality of subcarriers. In addition, each subframe may use certain subcarriers of certain symbols (e.g., a first symbol) of a subframe for a physical downlink control channel (PDCCH), that is, an L1/L2 control channel. The PDCCH carries scheduling assignments and other control information. In FIG. 5, an L1/L2 control information transmission area (PDCCH) and a data area (PDSCH) are shown. In one embodiment, a radio frame of 10 ms is used and one radio frame includes 10 subframes. In addition, one subframe includes two consecutive slots. The length of one slot may be 0.5 ms. In addition, one subframe includes a plurality of OFDM symbols and a portion (e.g., a first symbol) of the plurality of OFDM symbols may be used for transmitting the L1/L2 control information.

A time interval in which one subframe is transmitted is defined as a transmission time interval (TTI). Time resources may be distinguished by a radio frame number (or radio frame index), a subframe number (or subframe index), a slot number (or slot index), and the like. TTI refers to an interval during which data may be scheduled. For example, in the current LTE/LTE-A system, an opportunity of transmission of an UL grant or a DL grant is present every 1 ms, and the UL/DL grant opportunity does not exists several times in less than 1 ms. Therefore, the TTI in the legacy LTE/LTE-A system is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, which is a physical channel, using a DL-SCH which is a transmission channel, except a certain control signal or certain service data. Information indicating to which UE (one or a plurality of UEs) PDSCH data is transmitted and how the UE receive and decode PDSCH data is transmitted in a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with a radio network temporary identity (RNTI) “A” and information about data is transmitted using a radio resource “B” (e.g., a frequency location) and transmission format information “C” (e.g., a transmission block size, modulation, coding information or the like) via a certain subframe. Then, one or more UEs located in a cell monitor the PDCCH using its RNTI information. And, a specific UE with RNTI “A” reads the PDCCH and then receive the PDSCH indicated by B and C in the PDCCH information. In the present invention, a PDCCH addressed to a certain RNTI means that the PDCCH is CRC-masked with the certain RNTI. A UE may attempt to decode a PDCCH using the certain RNTI if the UE is monitoring a PDCCH addressed to the certain RNTI.

FIG. 6 is a diagram for medium access control (MAC) structure overview in a UE side.

The MAC layer supports the following functions: mapping between logical channels and transport channels; multiplexing of MAC SDUs from one or different logical channels onto transport blocks (TB) to be delivered to the physical layer on transport channels; demultiplexing of MAC SDUs from one or different logical channels from transport blocks (TB) delivered from the physical layer on transport channels; scheduling information reporting (e.g. scheduling request, buffer status reporting); error correction through HARQ; priority handling between UEs by means of dynamic scheduling; priority handling between logical channels of one MAC entity; Logical Channel Prioritization (LCP); transport format selection; and radio resource selection for sidelink (SL).

The MAC provides services to the RLC in the form of logical channels. A logical channel is defined by the type of information it carries and is generally classified as a control channel, used for transmission of control and configuration information necessary for operating an LTE system, or as a traffic channel, used for the user data. The set of logical channel types specified for LTE includes broadcast control channel (BCCH), paging control channel (PCCH), common control channel (CCCH), dedicated control channel (DCCH), multicast control channel (MCCH), dedicated traffic channel (DTCH), multicast traffic channel (MTCH).

From the physical layer, the MAC layer uses services in the form of transport channels. A transport channel is defined by how and with what characteristics the information is transmitted over the radio interface. Data on a transport channel is organized into transport blocks. In each transmission time interval (TTI), at most one transport block of dynamic size is transmitted over the radio interface to/from a terminal in the absence of spatial multiplexing. In the case of spatial multiplexing (MIMO), there can be up to two transport blocks per TTI.

Associated with each transport block is a transport format (TF), specifying how the transport block is to be transmitted over the radio interface. The transport format includes information about the transport-block size, the modulation-and-coding scheme, and the antenna mapping. By varying the transport format, the MAC layer can thus realize different data rates. Rate control is therefore also known as transport-format selection.

To support priority handling, multiple logical channels, where each logical channel has its own RLC entity, can be multiplexed into one transport channel by the MAC layer. At the receiver, the MAC layer handles the corresponding demultiplexing and forwards the RLC PDUs to their respective RLC entity for in-sequence delivery and the other functions handled by the RLC. To support the demultiplexing at the receiver, a MAC is used. To each RLC PDU, there is an associated sub-header in the MAC header. The sub-header contains the identity of the logical channel (LCID) from which the RLC PDU originated and the length of the PDU in bytes. There is also a flag indicating whether this is the last sub-header or not. One or several RLC PDUs, together with the MAC header and, if necessary, padding to meet the scheduled transport-block size, form one transport block which is forwarded to the physical layer.

In addition to multiplexing of different logical channels, the MAC layer can also insert the so-called MAC control elements into the transport blocks to be transmitted over the transport channels. A MAC control element is used for inband control signaling—for example, timing-advance commands and random-access response. Control elements are identified with reserved values in the LCID field, where the LCID value indicates the type of control information.

Furthermore, the length field in the sub-header is removed for control elements with a fixed length.

The MAC multiplexing functionality is also responsible for handling of multiple component carriers in the case of carrier aggregation. The basic principle for carrier aggregation is independent processing of the component carriers in the physical layer, including control signaling, scheduling and hybrid-ARQ retransmissions, while carrier aggregation is invisible to RLC and PDCP. Carrier aggregation is therefore mainly seen in the MAC layer, where logical channels, including any MAC control elements, are multiplexed to form one (two in the case of spatial multiplexing) transport block(s) per component carrier with each component carrier having its own hybrid-ARQ entity.

FIG. 7 is a diagram for a MAC PDU structure used in the LTE/LTE-A system. FIG. 8 are examples of MAC subheaders used in the LTE/LTE-A system.

A MAC PDU is a bit string that is byte aligned (i.e. multiple of 8 bits) in length. In FIG. 8, bit strings are represented by tables in which the most significant bit is the leftmost bit of the first line of the table, the least significant bit is the rightmost bit on the last line of the table, and more generally the bit string is to be read from left to right and then in the reading order of the lines. The bit order of each parameter field within a MAC PDU is represented with the first and most significant bit in the leftmost bit and the last and least significant bit in the rightmost bit.

MAC SDUs are bit strings that are byte aligned (i.e. multiple of 8 bits) in length. An SDU is included into a MAC PDU from the first bit onward. The MAC entity shall ignore the value of reserved bits in downlink MAC PDUs.

A MAC PDU consists of a MAC header, zero or more MAC service data units (MAC SDUs), zero, or more MAC control elements (MAC CEs), and optionally padding, as described in FIG. 7. Both the MAC header and the MAC SDUs are of variable sizes.

A MAC PDU header consists of one or more MAC PDU subheaders; each subheader corresponds to either a MAC SDU, a MAC control element or padding. Referring to FIG. 8, a MAC PDU subheader consists of the five or six header fields R/F2/E/LCID/(F)/L but for the last subheader in the MAC PDU and for fixed sized MAC control elements. The last subheader in the MAC PDU and subheaders for fixed sized MAC control elements consist solely of the four header fields R/F2/E/LCID. A MAC PDU subheader corresponding to padding consists of the four header fields R/F2/E/LCID.

In the LTE/LTE-A system, MAC PDU subheaders have the same order as the corresponding MAC SDUs, MAC control elements and padding. In the LTE/LTE-A system, MAC control elements are always placed before any MAC SDU.

Padding occurs at the end of the MAC PDU, except when single-byte or two-byte padding is required. Padding may have any value and the MAC entity shall ignore it. When padding is performed at the end of the MAC PDU, zero or more padding bytes are allowed. In the LTE/LTE-A system, when single-byte or two-byte padding is required, one or two MAC PDU subheaders corresponding to padding are placed at the beginning of the MAC PDU before any other MAC PDU subheader. A maximum of one MAC PDU can be transmitted per TB per MAC entity. A maximum of one MCH MAC PDU can be transmitted per TTI.

A fully mobile and connected society is expected in the near future, which will be characterized by a tremendous amount of growth in connectivity, traffic volume and a much broader range of usage scenarios. Some typical trends include explosive growth of data traffic, great increase of connected devices and continuous emergence of new services. Besides the market requirements, the mobile communication society itself also requires a sustainable development of the eco-system, which produces the needs to further improve system efficiencies, such as spectrum efficiency, energy efficiency, operational efficiency and cost efficiency. To meet the above ever-increasing requirements from market and mobile communication society, next generation access technologies are expected to emerge in the near future.

Work has started in ITU and 3GPP to develop requirements and specifications for new radio systems, as in the Recommendation ITU-R M.2083 “Framework and overall objectives of the future development of IMT for 2020 and beyond”, as well as 3GPP SA1 study item New Services and Markets Technology Enablers (SMARTER) and SA2 study item Architecture for the new RAT (NR) System (also referred to as 5G new RAT). It is required to identify and develop the technology components needed for successfully standardizing the NR system timely satisfying both the urgent market needs, and the more long-term requirements set forth by the ITU-R IMT-2020 process. In order to achieve this, evolutions of the radio interface as well as radio network architecture have to be considered in the “New Radio Access Technology.”

FIG. 9 illustrates an overall procedure of the MAC PDU construction process in the LTE/LTE-A system.

In the LTE/LTE-A system, a MAC PDU construction process at a UE starts when a UL grant is received, as follows.

-   -   1. The UE receives a UL grant from an eNB.     -   2. The MAC entity performs Logical Channel Prioritization (LCP)         procedure to determine the RLC PDU size for each RLC entity.     -   3. The MAC entity indicates the determined RLC PDU size to each         RLC entity.     -   4. Each RLC entity performs segmentation and/or concatenation of         RLC SDUs to construct a RLC PDU. For each RLC PDU, Framing Info         (FI) and RLC Sequence Number (RSN) are mandatorily present. The         Length Indicator (LI) is included each time two RLC SDUs         (segments) are concatenated.     -   5. Each RLC entity delivers the constructed RLC PDU to the MAC         entity.     -   6. The MAC entity concatenates RLC PDUs received from multiple         RLC entities.     -   7. The MAC entity sets the value of MAC subheader for each MAC         SDU, and collects all MAC subheaders in front of the MAC PDU to         form a MAC header.

The MAC PDU construction process in the LTE/LTE-A system has the following problems and/or redundancies. A UE can start the MAC PDU construction process only after the UE receives a UL grant. Especially, RLC segmentation and concatenation process starts only after the MAC entity indicates the RLC PDU size to the RLC entity, which takes long time before MAC PDU construction. Due to the variable length nature of MAC SDU and MAC subheaders, determining a RLC PDU size for each RLC entity is very complex. A MAC PDU cannot be delivered to the PHY until whole the MAC PDU is constructed, because all the MAC subheaders should be collected together and put into the front of the MAC PDU. In the meantime, in the LTE/LTE-A system, a PDCP SN is already included in a RLC SDU, and adding another SN in the RLC is redundant. The same function is spread over two layers (MAC and RLC), which is redundant and inefficient, since the RLC includes a LI field to indicate the length of RLC SDU (segment), and the MAC includes a L field to indicate the length of MAC SDU. Therefore, the present invention propose a new MAC PDU construction process for the NR system.

FIG. 10 illustrates an example of a MAC PDU construction process for the NR system according to the present invention.

The important point of the present invention is that a MAC at a transmitting side attaches a MAC subheader right after the end of a corresponding MAC SDU or MAC CE. In the present invention, with a MAC subheader interleaved with a corresponding MAC SDU or MAC CE, it is expected that MAC delivers the generated part of MAC PDU to PHY immediately after attaching a MAC subheader to a corresponding generated MAC SDU or MAC CE, even before generating whole MAC PDU, so that the PHY can start processing of the received part of MAC PDU quickly. Besides, in the present invention, a MAC at a receiving side can process the MAC PDU from the end of the MAC PDU to obtain MAC CE(s) and then process the remaining part of the MAC PDU to obtain MAC SDU(s). If a MAC subheader is attached at the beginning of each MAC SDU and MAC CE, a BS (e.g. gNB) has to process all MAC SDUs before identifying the MAC CEs. This burden is definitely not preferred in the BS side. In the meantime, if a MAC PDU includes MAC SDUs according to the present invention, the MAC SDUs would be obtained in reverse order of the construction order of the MAC PDU, which would lead to out-of-order PDU reception in RLC. However, the out-of-order PDU reception in RLC may not be a big problem because PDCP would anyway perform reordering.

For the convenience for the description, in the following description, the present invention is described using an example where a UE is a transmitting side and a BS or network is a receiving side, but the present invention is also applied in the same or similar manner even when a BS or network is a transmitting side and a UE is a receiving side, except that a UE should receive a UL grant used for MAC PDU transmission while a BS does not have to receive a DL grant used for MAC PDU transmission but can allocate it for itself.

If a UE is a transmitting side, the UE attaches a MAC subheader at the end of a corresponding MAC SDU or MAC CE. When the UE receives the UL grant, the UE constructs a MAC PDU by concatenating multiple sets of ‘MAC SDU+MAC subheader’ and/or ‘MAC CE+MAC subheader’, and transmits the MAC PDU using the received UL grant. The MAC subheader may include a logical channel ID (LCID) field which identifies the logical channel (or RLC entity) to which the corresponding MAC SDU belongs or identifies the type of MAC CE, and a length (L) field which indicates the length of the corresponding MAC SDU or MAC CE.

In the present invention, when the UE constructs the MAC PDU, the UE may include MAC CE(s) at the end of the MAC PDU. That is, the UE includes MAC SDU(s) first, and then includes MAC CE(s) in the MAC PDU. In a UE, some MAC CEs such as BSR or PHR need to reflect the latest UE status before transmission. For example, BSR MAC CE is placed at the beginning of MAC PDU as in the LTE/LTE-A system, the MAC at the UE can only deliver the MAC PDU after a complete MAC PDU is generated, because a BSR MAC can only be generated after placing all MAC SDUs, and the PHY needs to receive MAC PDU in order, i.e., from the beginning part, for the PHY layer processing. Placing the MAC CE at the end of a MAC PDU enables partial MAC PDU delivery to physical layer while gives more time to reflect the latest UE status in the MAC CE. In the receiving side, the placement of MAC CEs does not affect receiving process as the receiving process would start only after receiving a whole transport block. In the receiving side, especially if the receiving side is a scheduler, what is important is how fast the receiver identifies the placement of MAC CEs. It is because the receiving side could identify MAC CEs at the end of the MAD PDU even before receiving a whole transport block and perform scheduling fast based on the MAC CEs if the MAC CEs are not placed in the middle of the MAC PDU but placed at the end of the MAC CE.

There are multiple types of MAC CEs defined, e.g., buffer status report (BSR) MAC CE, power headroom report (PHR) MAC CE, DRX Command MAC CE, activation/deactivation MAC CE, etc. The placement order between MAC CEs are arbitrary, or defined by relative priority order for the LCP procedure (e.g. see the document 36.321 at section 5.4.3.1).

Referring to FIG. 10, the overall MAC PDU construction process in the UE may be explained as follows.

-   -   When the MAC entity receives UL grant from the BS (e.g. eNB or         gNB), the MAC entity performs a LCP procedure to allocate UL         resource to RLC PDU(s) (=MAC SDU(s)) and/or MAC CEs.     -   The MAC entity receives MAC SDU(s) from RLC entiti(es), and         attaches a MAC subheader at the end of each MAC SDU. The MAC         subheader includes a LCID field which identifies the logical         channel (or RLC entity) to which the corresponding MAC SDU         belongs, and a L field which indicates the length of the         corresponding MAC SDU. The placement order between LCID and L         fields are either L/LCID or LCID/L.     -   The MAC entity constructs MAC CE(s), and attaches MAC subheader         at the end of each MAC CE. The MAC subheader includes a LCID         field which identifies the type of MAC CE. The MAC subheader may         include a L field which indicates the length of the         corresponding MAC CE. The MAC subheader may or may not include a         L field which indicates the length of a MAC CE depending on the         type of the MAC CE. For example, a MAC CE of which length is not         fixed may include the L field, and a MAC CE of which length is         fixed may not include the L field. The placement order between         LCID and L fields are either L/LCID or LCID/L. If the L field         may or may not be included in a MAC subheader for a MAC CE, and         if the MAC PDU is processed at a receiver from the end of the         MAC PDU, it would be preferable that the LCID field may be         placed after the L field, in order for the receiver to determine         the presence or absence of the L field based on the LCID field.         The placement order between MAC CEs are arbitrary or defined by         the priority order of the LCP procedure.     -   The UE constructs a MAC PDU by concatenating ‘MAC SDU+MAC         subheader’ and/or ‘MAC CE+MAC subheader’. The UE includes ‘MAC         SDU+MAC subheader’ first, and then includes MAC CE+MAC subheader         at the end of the MAC PDU. In other words, as shown in FIG. 10,         the UE places ‘MAC SDU+MAC subheader” on the left side of ‘MAC         CE+MAC subheader’ in the MAC PDU and places ‘MAC CE+MAC         subheader’ in the right side of ‘MAC SDU+MAC subheader’ in the         MAC PDU.     -   The UE transmits the constructed MAC PDU to the BS (e.g. eNB or         gNB) using the received UL grant.

As mentioned before, attaching the MAC subheader at the end of MAC SDU or MAC CE, and/or including MAC CE(s) at the end of MAC PDU has following benefits. The transmitting side (e.g. UE) can process MAC SDUs for transmission without waiting for the MAC CE construction, and this will facilitate the fast MAC PDU processing in the transmitting side. A receiving side (e.g. BS) can easily identify a MAC CE by processing a MAC PDU from the end to start of the MAC PDU, and this will facilitate the fast MAC CE processing in the receiving side.

The present invention also applies to DL data transmission where the transmitting side is a BS and the receiving side is a UE.

FIG. 11. is a block diagram illustrating elements of a transmitting device 100 and a receiving device 200 for implementing the present invention.

The transmitting device 100 and the receiving device 200 respectively include Radio Frequency (RF) units 13 and 23 capable of transmitting and receiving radio signals carrying information, data, signals, and/or messages, memories 12 and 22 for storing information related to communication in a wireless communication system, and processors 11 and 21 operationally connected to elements such as the RF units 13 and 23 and the memories 12 and 22 to control the elements and configured to control the memories 12 and 22 and/or the RF units 13 and 23 so that a corresponding device may perform at least one of the above-described embodiments of the present invention.

The memories 12 and 22 may store programs for processing and controlling the processors 11 and 21 and may temporarily store input/output information. The memories 12 and 22 may be used as buffers.

The processors 11 and 21 generally control the overall operation of various modules in the transmitting device and the receiving device. Especially, the processors 11 and 21 may perform various control functions to implement the present invention. The processors 11 and 21 may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. The processors 11 and 21 may be implemented by hardware, firmware, software, or a combination thereof. In a hardware configuration, application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), or field programmable gate arrays (FPGAs) may be included in the processors 11 and 21. Meanwhile, if the present invention is implemented using firmware or software, the firmware or software may be configured to include modules, procedures, functions, etc. performing the functions or operations of the present invention. Firmware or software configured to perform the present invention may be included in the processors 11 and 21 or stored in the memories 12 and 22 so as to be driven by the processors 11 and 21.

The processor 11 of the transmitting device 100 performs predetermined coding and modulation for a signal and/or data scheduled to be transmitted to the outside by the processor 11 or a scheduler connected with the processor 11, and then transfers the coded and modulated data to the RF unit 13. For example, the processor 11 converts a data stream to be transmitted into K layers through demultiplexing, channel coding, scrambling, and modulation. The coded data stream is also referred to as a codeword and is equivalent to a transport block which is a data block provided by a MAC layer. One transport block (TB) is coded into one codeword and each codeword is transmitted to the receiving device in the form of one or more layers. For frequency up-conversion, the RF unit 13 may include an oscillator. The RF unit 13 may include Nt (where Nt is a positive integer) transmit antennas.

A signal processing process of the receiving device 200 is the reverse of the signal processing process of the transmitting device 100. Under control of the processor 21, the RF unit 23 of the receiving device 200 receives radio signals transmitted by the transmitting device 100. The RF unit 23 may include Nr (where Nr is a positive integer) receive antennas and frequency down-converts each signal received through receive antennas into a baseband signal. The processor 21 decodes and demodulates the radio signals received through the receive antennas and restores data that the transmitting device 100 intended to transmit.

The RF units 13 and 23 include one or more antennas. An antenna performs a function for transmitting signals processed by the RF units 13 and 23 to the exterior or receiving radio signals from the exterior to transfer the radio signals to the RF units 13 and 23. The antenna may also be called an antenna port. Each antenna may correspond to one physical antenna or may be configured by a combination of more than one physical antenna element. The signal transmitted from each antenna cannot be further deconstructed by the receiving device 200. An RS transmitted through a corresponding antenna defines an antenna from the view point of the receiving device 200 and enables the receiving device 200 to derive channel estimation for the antenna, irrespective of whether the channel represents a single radio channel from one physical antenna or a composite channel from a plurality of physical antenna elements including the antenna. That is, an antenna is defined such that a channel carrying a symbol of the antenna can be obtained from a channel carrying another symbol of the same antenna. An RF unit supporting a MIMO function of transmitting and receiving data using a plurality of antennas may be connected to two or more antennas.

In the embodiments of the present invention, a UE operates as the transmitting device 100 in UL and as the receiving device 200 in DL. In the embodiments of the present invention, an eNB operates as the receiving device 200 in UL and as the transmitting device 100 in DL. Hereinafter, a processor, an RF unit, and a memory included in the UE will be referred to as a UE processor, a UE RF unit, and a UE memory, respectively, and a processor, an RF unit, and a memory included in the eNB will be referred to as an eNB processor, an eNB RF unit, and an eNB memory, respectively.

The UE processor can be configured to operate according to the present invention, or control the UE RF unit to receive or transmit signals according to the present invention. The eNB processor can be configured to operate according to the present invention, or control the eNB RF unit to receive or transmit signals according to the present invention.

A processor of a transmitting device generates a medium access control (MAC) protocol data unit (PDU) according to present invention. The processor of the transmitting device controls the RF unit to transmit the MAC PDU. The processor of the transmitting device may generate or construct the MAC PDU such that the MAC PDU includes at least a MAC service data unit (SDU) and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC control element (CE) and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE. The processor of the transmitting device may include, in the first MAC subheader, a logical channel identity (LCID) field which identifies a logical channel or radio link control (RLC) entity to which the MAC SDU belongs, and a length (L) field which indicates a length of the MAC SDU. The processor of the transmitting device may include, in the second MAC subheader, a LCID field which identifies a type of the MAC CE. The processor of the transmitting device may further include, in the second MAC subheader, a L field which indicates a length of the MAC CE. The processor of the transmitting device may include, in the second MAC subheader, the LCID after the L field. The processor of the transmitting device may generate or construct the MAC PDU such that the MAC PDU includes the MAC SDU and the first MAC subheader before the MAC CE and the second MAC subheader. The processor of the transmitting device may generate or construct the MAC PDU such that the MAC PDU includes the MAC CE and the second MAC subheader in the end of the MAC PDU. If the transmitting device is a UE, the processor of the transmitting device generates the MAC PDU based on a UL grant received from a receiving side (e.g. BS), and controls the RF unit of the transmitting device to transmit the MAC PDU using the UL grant. If the transmitting device is a BS, the processor of the transmitting device may control the RF unit of the transmitting device to transmit a DL grant and control the RF unit of the transmitting device to transmit the MAC PDU using the DL grant.

A processor of a receiving device controls a RF unit of the receiving device to receive a MAC PDU, and process the MAC PDU according to the present invention. In the present invention, the MAC PDU includes at least a MAC SDU and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC CE and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE. In the present invention, the processor of the receiving device may process the MAC PDU from the end of the MAC PDU toward the start of the MAC PDU. The processor of the receiving device may process the MAC SDU based on the first MAC subheader, where the first MAC subheader includes a LCID field which identifies a logical channel or RLC entity to which the MAC SDU belongs, and a L field which indicates a length of the MAC SDU. The processor of the receiving device may process the MAC CE based on the second MAC subheader, where the second MAC subheader includes a LCID field which identifies a type of the MAC CE. The second MAC subheader may or may not include a L field, which indicates a length of the MAC CE, according to the type of the MAC CE. The second MAC subheader may include the LCID after the L field, and the processor of the receiving device may determine the presence or absence of the L field based on the LCID of the MAC CE. The processor of the receiving device may process the MAC PDU on the assumption that the MAC PDU includes the MAC SDU and the first MAC subheader before the MAC CE and the second MAC subheader. The processor of the receiving device may process the MAC PDU on the assumption that the MAC PDU includes the MAC CE and the second MAC subheader in the end of the MAC PDU. If the receiving device is a BS, the processor of the receiving device may transmit the RF unit of the receiving device to transmit a UL grant to a UE and control the RF unit of the receiving device to receive a MAC PDU using the UL grant. If the receiving device is a UE, the processor of the receiving device may control the RF unit of the receiving device to receive a DL grant and control the RF unit of the receiving device to a MAC PDU using the DL grant.

As described above, the detailed description of the preferred embodiments of the present invention has been given to enable those skilled in the art to implement and practice the invention. Although the invention has been described with reference to exemplary embodiments, those skilled in the art will appreciate that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention described in the appended claims. Accordingly, the invention should not be limited to the specific embodiments described herein, but should be accorded the broadest scope consistent with the principles and novel features disclosed herein.

INDUSTRIAL APPLICABILITY

The embodiments of the present invention are applicable to a network node (e.g., BS), a UE, or other devices in a wireless communication system. 

What is claimed is:
 1. A method for transmitting, by a transmitting device, a data unit in a wireless communication system, the method comprising: generating, by the transmitting device, a medium access control (MAC) protocol data unit (PDU); and transmitting, by the transmitting device, the MAC PDU, wherein the MAC PDU includes at least a MAC service data unit (SDU) and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC control element (CE) and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE, wherein the second MAC subheader includes a logical channel identity (LCID) field which identifies a type of the MAC CE, wherein the second MAC subheader includes a length (L) field which indicates a length of the MAC CE, and wherein the second MAC subheader includes the LCID field after the L field.
 2. The method according to claim 1, wherein the first MAC subheader includes a logical channel identity (LCID) field which identifies a logical channel or radio link control (RLC) entity to which the MAC SDU belongs, and a length (L) field which indicates a length of the MAC SDU.
 3. The method according to claim 1, wherein the MAC PDU includes the MAC SDU and the first MAC subheader before the MAC CE and the second MAC subheader.
 4. The method according to claim 1, wherein the MAC PDU includes the MAC CE and the second MAC subheader in the end of the MAC PDU.
 5. A method for receiving, by a receiving device, a data unit in a wireless communication system, the method comprising: receiving, by the receiving device, a medium access control (MAC) protocol data unit (PDU); and processing, by the receiving device, the MAC PDU, wherein the MAC PDU includes at least a MAC service data unit (SDU) and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC control element (CE) and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE, wherein the receiving device processes the MAC PDU from the end of the MAC PDU toward the start of the MAC PDU, wherein the second MAC subheader includes a logical channel identity (LCD) field which identifies a type of the MAC CE, wherein the second MAC subheader includes a length (L) field which indicates a length of the MAC CE, and wherein the second MAC subheader includes the LCD field after the L field.
 6. The method according to claim 5, wherein the MAC PDU includes the MAC SDU and the first MAC subheader before the MAC CE and the second MAC subheader.
 7. The method according to claim 5, wherein the MAC PDU includes the MAC CE and the second MAC subheader in the end of the MAC PDU.
 8. A transmitting device for transmitting a data unit in a wireless communication system, the transmitting device comprising: a radio frequency (RF) unit, and a processor configured to control the RF unit, the processor configured to: generate a medium access control (MAC) protocol data unit (PDU); and control the RF unit to transmit the MAC PDU, wherein the MAC PDU includes at least a MAC service data unit (SDU) and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC control element (CE) and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE, wherein the second MAC subheader includes a logical channel identity (LCID) field which identifies a type of the MAC CE, wherein the second MAC subheader includes a length (L) field which indicates a length of the MAC CE, and wherein the second MAC subheader includes the LCID field after the L field.
 9. The transmitting device according to claim 8, wherein the first MAC subheader includes a logical channel identity (LCID) field which identifies a logical channel or radio link control (RLC) entity to which the MAC SDU belongs, and a length (L) field which indicates a length of the MAC SDU.
 10. The transmitting device according to claim 8, wherein the MAC PDU includes the MAC SDU and the first MAC subheader before the MAC CE and the second MAC subheader.
 11. The transmitting device according to claim 8, wherein the MAC PDU includes the MAC CE and the second MAC subheader in the end of the MAC PDU.
 12. A receiving device for receiving a data unit in a wireless communication system, the receiving device comprising: a radio frequency (RF) unit, and a processor configured to control the RF unit, the processor configured to: control the RF unit to receive a medium access control (MAC) protocol data unit (PDU); and process the MAC PDU, wherein the MAC PDU includes at least a MAC service data unit (SDU) and a first MAC subheader of the MAC SDU which is attached immediately after the end of the MAC SDU, or a MAC control element (CE) and a second MAC subheader of the MAC CE which is attached immediately after the end of the MAC CE, wherein the processor is configured to process the MAC PDU from the end of the MAC PDU toward the start of the MAC PDU, wherein the second MAC subheader includes a logical channel identity (LCD) field which identifies a type of the MAC CE, and wherein the second MAC subheader includes a length (L) field which indicates a length of the MAC CE, and wherein the second MAC subheader includes the LCD field after the L field.
 13. The receiving device according to claim 12, wherein the MAC PDU includes the MAC SDU and the first MAC subheader before the MAC CE and the second MAC subheader.
 14. The receiving device according to claim 12, wherein the MAC PDU includes the MAC CE and the second MAC subheader in the end of the MAC PDU. 